Electrohydraulic brake



Sept. 20, 1949.

Filed Dec. 29, 1945 c. HOLLERITH 2,482,732

ELECTROHYDRAULI C BRAKE 2 Sheets-Sheet l EI-IIIIRLEE HULLEEITI'I' 751W ma A Sept. 20, 1949. c, HQLLERITH 2,482,732

ELECTROHYDRAULI C BRAKE Filed Dec. 29, 1945 2 Sheets-Sheet 2 I2! ,2 EHFIF'LEE HULLEFv'ITH 4 I25 film f-(iy Patented Sept. 20, 1949 2,482,732 ELECTROH'ZDRAULIO BRAKE Charles Hollerith, Jackson. Mioh.,

mesne assignments, to The B. F.

assignor, by Goodrich Company, Akron, Ohio, a corporation of New York Application December 29, 1945, Serial No. 838,818

Claims. (CL 188-152) The present invention relates to hydraulic systems and more particularly to an electro-hydraulic system for actuating wheel brakes.

The invention is particularly applicable to airplane wheel brakes. In prior art airplane wheel brake systems the usual custom is to provide pressure accumulators for hydraulic fluid and long lines therefrom to the brakes. The long lines have the disadvantage of not only exposing long pressure lines to possible leakage but also result in a delay in the operation of the brake. Furthermore, long pressure lines will increase cost and weight of the installation.

The present invention eliminates the enumerated prior art difficulties in that it provides a compact unit which may be operated by remote control and located adjacent the wheel brakes to be operated. The unit, according to the present invention, is made compact by disposing a pressure-developing ump within the hydraulic fluid reservoir and mounting the controlling valve mechanism on the reservoir.

Accordingly, an object of the present invention is to provide an electro-hydraulic brake system as a compact unit.

Another object of the invention is to provide a hydraulic system of compact size which may be mounted adjacent the brake to be actuated.

Another object of the invention is to provide a compact hydraulic brake unit, adapted to be operated by remote control.

Still another object of the invention is to provide a hydraulic brake unit wherein there is a reservoir in which there is disposed a pressuredeveloping pump for forcing hydraulic fluid into the system and a differentially controlled by-pass valve for controlling the pressure applied to the brake.

A further object of the invention is to provide in a hydraulic system of the character described a so-called parking valve for trapping in the system, hydraulic fluid at full pressure, to maintain the brake applied.

These and other objects residing in the arrangement, combination and construction of the parts will be apparent from the following specification and claims, when taken with the accompanying drawings, in which Fig. 1 is a diagrammatic illustration of a hydraulic system according to the present invention, Fig. 2 is a vertical section through a specific form reservoir and valve-controlling structure, and

Referring particularly to Fig. 1 of the drawings,

Fig. 3 is a section on the line m-nr of Fig. 2.

it against a seat 88 to close the by-pass established the reference character I indicates a pump which is driven by a motor 2 and is arranged to force hydraulic fluid from the reservoir 2| under pressure through a conduit 3. The conduit 3 includes a portion 4 at the right-hand end of a cylinder 8 as viewed in Fig. 1 but also includes a tube 8 which delivers hydraulic fluid under pressure through a pressure regulator 'l and a distributing tube 8 communicating with expander tubes 8 and III of a brake generally indicated at H, having a brake shoe l2 and brake blocks l8 and it.

The brake II is actuated by hydraulic pressure fluid from the distributor 8 expanding the tubes 8 and It to force the brake blocks l3 and it outwardly into contact with the drum i2. Upon a decrease in the hydraulic fluid pressure, as when the brake control is released, the expander tubes 8 and I8 collapse and the brake blocks l3 and I4 retract from the drum l2 in a manner which is well known in the art. In order to provide the proper degree of clearance between the brake blocks l8 and I4 and the drum i2 and at the same time to retain a predetermined amount of hydraulic fluid in the distributor 8 and the expander tubes 8 and I0, there is provided the pressure regulating valve I.

Pressure regulating valve 1 consists of a housing l8 in which is mounted a diaphragm l8. The diaphragm I8 is urged against a seat 20 by a spring 2| bearing against a piston 22 in a cylinder 28. The pressure exerted by the spring 2i is adjustable by means of a screw 24. The tube 8 terminates in a port 25 which is sealed oil by diaphragm l8 when it is seated against the seat 28.

Upon release of the brake H by reducing the hydraulic fluid pressure as hereinafter described,

hydraulic fluid in the distributor 8 will escape therefrom and from the expander tubes 8 and Ill until the diaphragm l9 under the action of the spring 28 closes the distributor 8 and the port 25. Thus the amount of pressure that is retained in the distributor 8 when the brake controls are released may be adjusted by means of the screw 24 controlling the tension on the spring 2|.

The pump i, if operating with the brake not applied, circulates hydraulic fluid through the portion 4 of the conduit 8, the conduit 21 and the port 28, back to the conduit 3, which passages constitute a by-pass of the hydraulic fluid from the normal channel for hydraulic fluid through the conduit 3 including the tube 6.

When it is desired to force hydraulic fluid under pressure into the tube 8 of the conduit 8 and to the distributor 8, a valve 28 is caused to seat '28 is maintained in a projected position with respect to the piston 3| by a helical spring 35 about the portion of the tube 35 projecting outwardly from the piston 3|. The norma1 'unstressed position of the piston 3| is established by a helical spring 31 bearing against one end thereof and hearing at the other end against a shoulder 38 comprising one end of the cylinder 5. The position of the piston 3| is also established by a helical spring 38 bearing against the opposite end of the piston 3| and against a piston 45. Pistons 3| and 45 are both slidable in the cylinder and are provided with suitable sealing rings for preventing the escape of hydraulic fluid therepast. The piston 45 in normal unstressed position is seate against a seat 43 at the left end of the cylinder 5 as viewed in Fig. l and has projecting outwardly therefrom, through a bore 44, a rod 45 having'contacts 45, 45 on an arm 41, 41 adapted to engage with contacts 48, 48 when the piston 45 moves to the right to close a circuit for driving the motor 2 for operating the pump The circuit 49 consists of conductors 52 and 53 having the contacts 48, a relay 54, a conductor 55 to ground and a conductor 55 through a battery 51 to the ground. The relay 54 closes a switch 55 which closes the motor 2 circuit which consists of ground, battery 51, conductor 55, the switch 55 and the motor 2 to ground.

Valve 33 is actuated by either of the foot pedals 5| or 52 which provide for dual control. The foot pedals 5| and 52 are both pivoted about pins 53 and have pivoted thereto rods 54. The rods 54 carry valves 55 arranged to close, upon lowering, ports 55 in pistons 51 in cylinders 58. Downward movement of the valves 55 and thus the pedals 5| and 52 is resisted by helical springs 58 in the cylinder 58 beneath the pistons 51. Ports 15 are provided in the structure of the valves 55 to permit the flow of hydraulic fluid from the portions of the cylinders 58 containing the springs 59 when pressureis removed from the pedals 5| and 52.

A supplementary hydraulic fluid reservoir 14 is provided having a conduit 15 communicating with the portion of the cylinder 58 0f the pedal 52 above the piston 51 therein, for maintaining the pedal system filled with fluid. Pressure on the pedal 52 results in forcing hydraulic fluid from its cylinder 58 through a conduit 15 into the top of the other cylinder 58 from which it flows through the port 55 thereof and the lower portion of its cylinder 58 through a conduit 11 into the end 18 of the cylinder 5.

Hydraulic fluid in the end 18 of the cylinder 15 forces the piston 45 to the right as viewed in Fig. 1. This force is transmitted through the spring 38 to the piston 3|. Resistance to movement to the right of the piston 3| is oflered by the spring 31. Relative movement between the pistons 45 and 3| is permitted because of the port in the tube 35 permitting escape and return of fluid from between the pistons 45 and 3|.

The spring 35 urges the valve 33 to the right to seat against the seat 35a to close the port 21, therefore preventing the by-passing of hydraulic fluid from the pump I through the port 28 back to the inlet of the pump The result is that hydraulic fluid from the pump I through the conduit 3 is directed past the tube 35 through the tube 5 to the distributor 8 to actuate the brake The closing of the contacts 45 and 48 should be timed to start the pump prior to the closing of the valve 28 to permit the pump to get up pressure first.

The hydraulic fluid in the conduit 3 when under pressure exerts a pressure against the piston 3| which force is transmitted through the spring 38 and the piston 45 back to the foot of the operator on pedal 5| or 52, depending upon which pedal is employed to initiate braking action. Thus, it will :be apparent that if only a slight pressure is placed on either the brake pedal 5| or 52, the pressure of the fluid of the distributor 8 will be slight and a substantial part of the hydraulic fluid pumped will be by-passed through the conduit 21 and the port 28 to the intake of the pump In order to increase the pressure of the fluid in distributor 8 it will be necessary to apply additional force to the brake pedal 5| or 52, depending on whichone is being used to overcome the tendency of the pressure in the conduit 3 to move the piston 3| and thus the piston 45 to the left. In this manner there is imparted to the foot of the operator on the brake pedal 5| or 52 a feel" which is indicative of the amount of pressure in distributor 8. In this way the operator may control, by the pressure of his foot, the amount of braking force applied to the brake.

In the event that it is desired to actuate the brake manually rather than by the remote hydraullc control provided by the pedals 5| and 52 and the conduits 11, there is provided a manual control.85 on the outer end of the rod 45. It will be thus obvious that by pushing the control to the right as viewed in Fig. 1 the contacts 45 and 48 will be closed to actuate the motor 2 and the pump and the pistons 45 and 3! --will be moved to the right to close the valve 29. It is contemplated that, if desired, suitable mechanical linkage connections may be made to control 85 for actuating the same if it is not convenient to employ the short control adjacent the cylinder 5 as shown diagrammatically in Fig. 1.

Another feature of the invention is the so-called parking valve 8|. Valve 8| is arranged in the conduit 3 and is adapted to seat against a seat 82 to close the conduit 3 to seal full pressure therein and in the distributor 8 to maintain the brakes applied for parking the vehicle, as for instance an airplane, with which the brakes are associated. The parking valve 8| is controlled by a solenoid 83 under the control of a, switch 84. The circuit for the solenoid 83 and the switch 84 consistsof ground through the battery 51, a conductor 85, switch 84, and a conductor 55 through the solenoid 83 to ground.

The structure disclosed hereinabove is considered to be a diagrammatic representation of the invention and of one form which the controlling valve may take. Another form of controlling valve which may be used in the system and which is considered to be diagrammatically represented by Fig. 1 is disclosed in Figs. 2 and 3.

In Figs. 2 and 3, the reservoir 88, provided with cooling fins 83, contains hydraulic fluid. In the reservoir 88 is arranged a pump 55 driven by a motor 3| partly broken away as shown in the drawing. The reservoir 88 is provided with filling and breathing device 81.

. outlet 94.

4 entering the port 2,

The pump 99 is provided with an inlet 99' as shown particularly in Fig. 3. Thedelivery side of the pump is connected to a conduit 92 which consists of a port 99, a connector 94 and appropriate tubing to the brake structure not shown but corresponding to the tubing 9 and distributor 9ofFig. 1. Theport99isina-block99securedto the reservoir 99 and is adjacent a cylinder 99 with which there is communication through a port 91.

There is provided a by-pass from the conduit 92, through the port 91, cylinder 99 and a conduit 99 to the reservoir 99, providing an endless circulation of brake fluid when the pump 99 is running and the brakes are not being operated.

There are disposed in the cylinder 99, pistons 99 and I corresponding respectively to the pistons 40 and 9| of Fig. 1. The piston I09 is provided with an opening IOI about which is a seat I02. The opening IOI comprises a part of the by-pass from the conduit 92 including the conduit 99, from the output side of the pump 90 to the reservoir 99.

The opening IOI is arranged to be closed under predetermined conditions of operation by a ball valve I fixedly carried on the end of a slidable rod I05. The rod I06 is provided with a suitable sealing ring I01 and is urged inwardly to move the ball I05 toward the seat I02 by the action of spring I09. Inward movement of the rod I09 is limited by nuts I09.

The pistons 99 and I00 are maintained in a predetermined'normal position by a helical spring IIO disposed between them and a helical spring III disposed between piston I00 and the right end of the cylinder 99 as viewed in F18. 1. I

The by-pass is arranged to be closed by pressure fluid from the brake pedals 9i and 92 as disclosed in Fig. 1, forcing hydraulic fluid through the conduit I'I through a port I I2 communicating with the space II3 between the left end of the cylinder 96 as viewed in Fig. 2, and the piston 99. The switch for starting the motor 9i to drive the pump 90 and corresponding to contacts 49 and 49 of Fig. 1, is controlled by a rod II4 disclosed in dotted outline in Fig. 2, which is moved axially by a cammlng surface I I3 cut in a rod I I9 extending axially from the piston 99.

When hydraulic fluid from some control means.

such as the pedals BI and 92 of Fig. 1 is directed through the port I I2 under pressure, it moves the piston 99 to the right as viewed in Fig. 2 and thus moves the spring H0 and the piston I00 to move the seat I02 against the ball I05 to close the by-pass valve. The by-pass valve consisting of seat I02 and the ball I05 is normally open sufflciently so that as the switch rod H4 is moved to closed position and the pistons 99 and I00 move to the right pump 90 will start and cause a circulation of hydraulic fluid through the conduit 92 and the port 91, the opening "I, the cylinder 99, and the conduit 99 to build up workin pressure in the outlet of the pump 90 before the seat I02 moves against the ball I05. Further movement of the piston I90 to the right causes the by-pass to be closed with the result that hydraulic fluid from the pump 99 is directed into the brake system through the It is tobe understood that as pressure is developed in conduit 92, pressure is eflective against the piston I00 and the ball I05 to move the same axially apart to permit bypassing a portion of the brake fluid. This force against the piston I00 is I I0 and the piston 99, through the hydraulic fluid back of the foot 0! the 99 into the reservoir transmitted through the spring 6 operator on the brake pedals 9i and. of 1. To increase the fluidpressure at the mtlet 94, further pressure applied to the brake pedal causes further force against the piston 99 to resuit in greater against the by-passing pressure valve. It will beunderstood that both the piston I00 and ball I99 are subjected to the pressure of the fluid in conduit 92, but that as the movement of the piston I99 to the right, as viewed in Fig. 2, is continued, the pressure which it is necessary to apply to the brake pedal will increase and the amount of hydraulic fluid by-passed will decrease. The result is that, as explained with respect to Fig. 1, the amount of braking action applied to the brake is varied according to the pressure on the brake pedal.

The structure in Figs. 2 and 3 is provided with a parking valve I20 corresponding to the parking valve 9I in Fig. 1. The parking valve I29 is mounted on an axially slidable rod I2I and is urged away from the seat I22, with which it is adapted 'to cooperate, by a helical spring I29. The parking valve I20 is in the conduit 92 between the by-pass valve and the pressure regulating valve I9 as disclosed in Fig. 1 and is adapted, as was the parking valve 8I of Fig. 1, to seal the braking fluid under pressure inthe brake system to maintain the brake in On condition for parking purposes.

The parking valve I20 is actuated by a rod I24 which is in turn operated by a solenoid, not shown,

' corresponding to the solenoid 99 of Fig. 1. The

rod I24 is pivoted by a pin I25 to the valve I29. Both the rods I2I and I24 are provided with suitable sealing rings I26 to prevent the escape of brake fluid.

There is disclosed in Fig. 2 a pressure releasing valve not disclosed in Fig. l but with which the structure of Fig. 1 may be provided if desired. The pressure releasing valve indicated generally at I21 consists of a ball I bearing against a seat I29. The ball I90 is urged against seat I29 by a plunger I29 slidable in a cylinder Ill and stressed by a spring I92. The tension of the spring I92 is adjustable by a screw I99. The pressure releasing valve is in a by-pass' consisting of a port I99 providing communication between the cylinder 90 and the cylinder I9I and a port I91 providing communication between the cylinder Ill and the portion of the conduit 92 adjacent the parking brake valve I20.

The tension of the spring I92 is adjusted to permit the pressure fluid in the conduit 92 to bypass to the cylinder 99, and thus through the conduit 99 into the reservoir 99, upon the pressure in the conduit 92 reaching a predetermined maximum value.

The valve and reservoir structure as disclosed in Figs. 2 and 3 is provided with suitable bleeder ports not shown for the purpose of venting air 1 The invention as disclosed fllustrates .in detail one form of valve unit that may be employed. Another form is illustrated diagrammatically. It will be understood that the other specific forms which will be apparent to those skilled in the art may be used without departing from the spirit and scope or the invention. Accordingly, I do not wish to be limited except by the scope or the following claims.

Having thus described my invention, what I desire to secure by Letters Patent and claim is:

1. An electric-hydraulic brake system for the landing wheels 01 airplanes and the like comprising a hydraulic brake, a supply 01' brake fluid located directly adjacent said brake, an electric operated hydraulic pump, conduit structure hydraulically connecting said brake, pump and supply,

landing wheels of airplanes and the like com-' prising a hydraulic brake, an electric driven pump, a fluid connection between said brake and the discharge of said pump, a hydraulic supply, a fluid connection between said brake and said supply, a by-pass connection between the inlet and discharge of said pump, valve mechanism for regulating said by-pass and the flow of fluid between said brake and said supply, means for operating said valve mechanism including means movable by fluid pressure and operatively associated with said valve mechanism, fluid displacement means, a hydraulic connection between said first and second means adapted to actuate said valve mechanism hydraulically to close said bypass to direct fluid pressure into said brake, an electric circuit for said pump, and switch means in said circuit and operatively associated with said valve mechanism for hydraulic actuation therewith.

3. An electric-hydraulic brake assembly comprising an electric drive pump having an inlet and a discharge, a by-pass conduit between said inlet and discharge, a valve regulating said bypass, a brake hydraulically connected to said discharge, means for hydraulically actuating said valve, an electric circuit for said pump, and a switch in said circuit operatively connected to said means.

4. As an article of manufacture, a unit for use in electric-hydraulic brake systems comprising a brake valve, a supply tank disposed at said brake, an electric pumping unit disposed in said tank having an inlet connection therewith, a discharge connection between said pump and said valve, a supply connection between said valve and said tank, a hydraulic actuator for said valve, and a switch mechanism associated with said valve for actuation by such actuator.

5. An electric-hydraulic brake system for landing wheels on aircraft comprising a brake, a pump, supply and brake valve unit located directly adjacent said brake and hydraulically connected thereto, and a remotely located manually controlled means hydraulically connected to said brake valve for actuating it, an electric circuit for said pump, and a switch in said circuit actuated in timed relation to the operation of said valve including a switch contact mounted on and movable with said valve.

CHARLES HOLLERITH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,110,567 McAulay Sept. 15, 1914 1,486,553 Mufliy' Mar. 11, 1924 1,744,684 Griflith Jan. 21, 1930 2,078,479 Briggs Apr. 27, 1937 2,273,152 Sonnlag Feb. 17, 1942 2,280,291 Jaseph Apr. 21, 1942 2,283,271 Loomis May 19, 1942 2,374,909 Williams May 1, 1945 

